P1137: ACCURACY AND PROGNOSTIC IMPACT OF FDG PET/CT AND BIOPSY IN BONE MARROW ASSESSMENT OF FOLLICULAR LYMPHOMA AT DIAGNOSIS: A NATION-WIDE STUDY.
Authors: I. Ródenas Quiñonero, T. Chen-Liang, T. Martín-Santos, A. Salar, M. Fernández-González, C. Celades, J. T. Navarro, A. B. Martinez, R. Andreu, A. Balaguer, A. Martín, M. Baile, J. López-Jiménez, J. Marquet, A. I. Teruel, M. J. Terol, C. Benet, L. Frutos, J. L. Navarro, J. Uña, M. Suarez, M. Cortes, J. Contreras, C. Ruiz, P. Tamayo, J. Mucientes, P. Sopena, L. Reguilón-Gallego, J. J. Sánchez-Blanco, E. Pérez-Ceballos, A. Jerez, F. J. Ortuño
Journal: HemaSphere (2022)

Background: In the workout of Follicular Lymphoma (FL), bone marrow biopsy (BMB) assessment is a key component of FLIPI and FLIPI2, the most widely used outcome scores. During the previous decade, several studies explored the role of FDG-PET/CT for detecting nodal and extranodal disease, with only one large study comparing both techniques. Aims: The aim of this study was to evaluate the diagnostic accuracy and the prognostic impact of both procedures in a retrospective cohort of 299 FL patients. Methods: Two hundred and ninety-nine, ≥18 y.o. patients diagnosed with FL between June 2005 and December 2018 were included. We used the Kaplan-Meier and the Cox method to analyze overall survival (OS) and progression free survival (PFS). To avoid collinearity in the multivariate regressions, we deconstructed the FLIPI2 composite in its foundational factors, considering bone marrow involvement (BMI) by mean of different measures in four models: BMB+, PET/CT+, “BMB+ and PET/CT+” and “BMB+ or PET/CT+”. In Cox regressions, examination of log (-log) survival plots ant partial residuals was performed to assess that the underlying assumption of proportional hazards was met. Results: The median follow-up was 57.3 months (range 3.6-185.8 months). The PET/CT was positive in 58 patients and negative in 238. Among those positive, 37 also had a BMB+, whereas 151 patients had a BMB+ with a PET/CT-. The BMB was positive in 124 patients and negative in 172. Among those negative, 21 had a PET/CT+. Considering PET/CT, the sensitivity was 63.7% (95% confidence interval(CI);50.5-77.0), specificity was 63.4% (95%CI;57.1-69.7), negative predictive value (NPV) was 87.7% (95%CI;82.6-92.9), accuracy 63.5% (95%CI:57.8-69.1). Focusing BMB, the sensitivity was 29.8% (95%CI;21.3-38.3), specificity was 87.7% (95%CI;82.6-92.9), NPV was 63.4% (95%CI;57.1-63.7) and accuracy was 63.5% (95%CI:57.8-69.1). Either beta2-microglobulin (B2M) over the upper normal limit (ULN), a diameter of the largest involved node (LoDLIN) over 6cm and a hemoglobin lower than 120g/L, were significantly associated with a shorter PFS in the univariate analysis. Also in univariate, a positive BMB and the combined “PET/CT or BMB positive”, were significantly associated with a shorter PFS. Neither BMI positive or the combined “PET/CT or BMB positive”, could add an independent prognostic value to the two factors than remained significant in the multivariate model: B2M higher than ULN and a LoDLIN over 6cm. Regarding OS, an elevated B2M, a LoDLIN over 6cm, a hemoglobin lower than 120g/L and an age older than 60y.o., were significantly associated with a shorter OS in the univariate analysis. A positive result by BMB, a positive PET/CT and the combined “PET/CT or BMB positive” result, were significantly associated with a shorter OS in univariate regression. The combined “PET/CT or BMB positive” and an age older than 60y.o. remained significant for a shorter OS in the multivariate model (p=0.030, HR 2.318, 95%CI 1.083-4.961 and p= 0.020, HR 2.473, 95%CI 1.151-5.314, respectively). Image:Summary/Conclusion: In our FL series, the combined “PET/CT or BMB positive” was the only BMI variable that showed an independent prognostic value in FL. Therefore, our data support that both procedures should be carried out in the upfront work of all suitable FL patients.